If using raw yam, boil it until just tender. I microwaved the frozen yam for couple of minutes.
Heat coconut oil in a pan, add the mustard seeds and once the seeds start to splutter, add the onion, garlic and curry leaves. Saute till onion turns golden.
Add chili powder, salt and pepper. Next add the yam and mix well to coat with the spices.
Cook on medium-low flame, stirring occasionally, until yam is crispy on the outside. Serve hot with rice.